In MLB, an alternate game jersey generally refers to something other than home white and road grey, but not a single-game jersey (JR Day, TBTC). Examples would be Cubs blue, White Sox black, Mets black, Reds red, Royals blue, Rays sky blue, and Twins dark blue, among others. A few teams have home and road alternates...Athletics gold and green (and black pre-2011), Braves red (home) and dark blue (road) and a handful of others.

Dave Miedema